1. Field of the Invention
The present invention relates to an electromagnetic contactor containing fixed contact pieces and a movable contact piece in a contact housing.
2. Description of the Related Art
Patent Document 1 discloses a contact device, which is an electromagnetic contactor used in a high voltage DC power supply circuit for electric vehicles and hybrid vehicles. This contact device comprises a contact mechanism that forms an electric path, an electromagnet device that opens and closes the contact mechanism, and a sealed case that houses the contact mechanism and the electromagnet device. At the both sides of the electromagnet device in the direction parallel to the electric path, a partition wall is formed to provide a vent passage between the partition wall and the sealed case. The contact device further comprises a permanent magnet disposed on the inner surface parallel to the electric path of the sealed case, the magnet generating a magnetic field to force an arc developing on the opening process of the contact mechanism toward the vent passage.
Patent Document 1    Japanese Patent No. 3997700
In the conventional example of Patent Document 1, the permanent magnet is disposed near the contact mechanism in the sealed case, thus a small permanent magnet can produce a sufficiently high magnetic flux density at the contact point of the contact mechanism. However, the arc that is extended toward the arc space near the inner surface of the sealed case may experience only a small or even an opposite-direction magnetic field produced by the small magnet. As a result, DC interruption may be impossible or an arc voltage needed for the DC interruption may make the arc space so large that the sealed case becomes an unallowably large scale. To ensure extinguishing the arc, the contact device of Patent Document 1 is provided with a vent passage at the side of the magnet device, and the arc is extended toward the vent passage, which requires a large electromagnet, enlarging the overall device size.